I agree with Nolan. I prefer the staples. Let's say a Client wants to buy a painting and take it with them on the aeroplane, but the frame is a problem. I just take a screwdriver, remove all the staples, roll it up so that they can put it a cylindrical cardboard holder. They can re-stretch it when they arrive at their destination. (Just roll it with the painting to the outside and NOT the other way around as you would normally expect). The other one with the insert is not easy to re-stretch. The staples are the most common type.

The canvasses with the staples on the sides are intended to be used with framing, so, if you intend to not use framing, then use only canvasses that have staples at the back. This allows clean sides for painting.